Method of preventing intrusion of toxic vapor into indoor air

ABSTRACT

Methods of preventing intrusion of toxic vapor into a building&#39;s interior air space. Contaminants operative to diffuse through a building&#39;s foundation and contaminate a building&#39;s interior air space are first determined. Once identified, the building&#39;s foundation, typically formed of concrete, will first be prepared for surface treatment followed by an application of at least one coating of a material suitable for imparting chemical resistance in the concrete. Such material may include novolac, vinyl novolac and related resin-based epoxy coatings. Such coatings, once applied, provide a protective barrier from commonly encountered contaminants, including a wide variety of volatile organic compounds. Such coatings are further expected to last the life of the building, or until physical wear requires repair or replacement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/576,546, entitled METHOD OF PREVENTING INTRUSION OF TOXIC VAPOR INTO INDOOR AIR, filed on Dec. 16, 2011, all of the teachings of which are incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

The present invention is directed to methods for preventing the intrusion of toxic and/or carcinogenic vapors that can permeate through the foundation and flooring of buildings and subsequently pose a potential health risk. In this regard, the methods of the present invention are operative to prevent the infiltration of vapors generated from a contamination source beneath the foundation and flooring of buildings that, per conventional practices, cannot be easily accessed and/or effectively removed.

Historical releases of toxic chemicals into the environment, particularly into soil and groundwater, present an ongoing risk to human health and local ecosystems. In many cases, the contaminated soil and groundwater can be cleaned by in-situ remediation processes, or soil can be dug up, hauled to a toxic waste facility, and clean soil can be applied to fill the hole. These methods are practical and cost effective for many sites, allowing land to be cleaned of toxic contaminants before construction of new buildings on the site.

However, in some cases contamination has been released or has spread through soil and groundwater and resides under an existing structure. Residual underground contamination (in soil and groundwater) can release toxic vapors to the indoor air of buildings, thus presenting a health risk to the building occupants. Chemical vapors (for example petroleum compounds like benzene or chlorinated solvents including tetrachloroethylene) can enter the building through cracks in concrete flooring or can uniformly permeate through the concrete slab.

Accordingly, there is a substantial need in the art for a method that can safely and effectively prevent potentially harmful vapors from permeating through the foundation and flooring of an existing building to thus protect the quality and safety of indoor air from toxic contaminant vapors emanating from the underlying soil and groundwater. There is likewise a need in the art for such a method that can be readily deployed, is cost effective and further operative to substantially eradicate the potential threat to human health and potential liability that presently cannot be addressed.

BRIEF SUMMARY

The present invention specifically addresses and alleviates the above-identified deficiencies in the art. In this regard, the present invention is directed to means of protecting the quality and safety of indoor air from toxic contaminant vapors in underlying soil and groundwater. According to a preferred embodiment, this invention provides a synergistic chemical resistance by absorbing a first coating into the concrete forming the foundation of a building and which rests upon a toxic contaminant source whereby the material inhibits chemical permeation within the concrete. At the same time, the invention assists adhesion of a continuous second coating (or topcoat) chemical barrier. According to a preferred embodiment, the first coating applied to the concrete comprises a two-part resin-based epoxy coating, such as novolac, vinyl novolac, or other chemically-resistant two-part Bisphenol A or Bisphenol F-based epoxy system (i.e., resin and hardener) as known in the art. The first coating material is of a thin consistency, capable of soaking into the concrete, and is applied in a single coat. After curing of the first coating, the topcoat is applied in one or more applications to yield a continuous, chemically-resistant epoxy barrier. In an exemplary application, the first coating may be applied having a thickness from 5-20 mil in thickness followed by a topcoat of 5-150 mil, preferably 10-40 mil.

The combination treatment results in a concrete that has chemical-resistant properties and a strongly-adhered chemically resistant barrier that inhibits both diffusion and advection of contaminated air and contaminants into the building. In this regard, such coatings are operative to provide protection against a wide variety of contaminants that would otherwise be operative to vaporize from beneath the foundation, rise up therethrough and provide a source of contamination. In this regard, it is contemplated that the present invention will be specifically directed to a variety of organic compounds that are capable of and in fact easily transition to a vapor phase, and include such well known contaminants as tetrachloroethylene, trichloroethylene, benzene, toluene, and a wide variety of volatile organic compounds. Advantageously, the methods of the present invention are operative to not only provide a protective barrier, but should do so for the life of the building or until physical wear requires repair and/or replacement of the foundation or the coating system.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:

FIG. 1 is a cross-sectional view of a building having a concrete foundation that defines an interior air space and wherein the foundation is built upon a source of contaminants operative to defuse through the foundation and contaminate the interior air space.

FIG. 2 is a schematic diagram illustrating the steps necessary for performing the methods of the present invention, as per a preferred embodiment.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be implemented or performed. The description sets forth the functions and sequences of steps for practicing the invention. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments and they are also intended to be encompassed within the scope of the invention.

Bearing the foregoing in mind, and referring now to FIG. 1, there is illustrated a structure 10 having sidewalls 20, 30 and ceiling 40 and defining an interior air space 50.

The building 10 is built upon foundation 60, the latter of which will typically comprise a slab of concrete or reinforced concrete, which may or may not include additional supportive structure such as rebar and the like, that, as is well-known to those skilled in the art, that defines a planar surface upon which the structure 10 is built. The building 10 as shown is further built upon an area of land 70 that includes contaminants represented as 80. Such contaminants, which for purposes of the present invention will include any organic contaminant operative to permeate through the slab 60, are indicated by the letter “A”, and thus create contamination in the air space 50.

This invention is a method for prevention of permeation of toxic vapors into structures with concrete floors comprising the steps and sequences as set forth in the flow chart diagram of FIG. 2. According to such method 100, the initial step 120 comprises determining the presence of contamination under an existing structure. As is well-known in the art, contaminants would typically have been deposited, spilled, or otherwise released into soil and groundwater accidentally or intentionally in the course of industrial activity, including manufacturing, degreasing, or as a result of leaks from pipes or storage tanks for fuels or chemicals. Identification and quantification of contamination under a structure would be accomplished by standard methods for environmental soil, groundwater, and air analyses from samples collected below or adjacent to the existing structure. These methods include systematic sampling of soil, water, and air, followed by analysis by standardized methods, e.g. Gas Chromatography/Mass Spectrometry (GC-MS).

As discussed above, the present invention is exceptionally effective in preventing toxic contaminant vapors that are organic in nature. Along those lines, this invention provides protection from commonly encountered contaminants including tetrachloroethylene, trichloroethylene, dichloroethylene isomers, vinyl chloride, benzene, toluene, ethylbenzene, xylene isomers, and other chlorinated and petroleum VOCs (volatile organic compounds). Once the presence and degree of contamination of the ground upon which the foundation rests has been determined, in 120, the floor surface is then prepared to accept a chemically-resistant treatment agent and topcoat at step 130. To prepare the concrete surface for the first coating, the floor should be swept clean of any dirt and debris. Additional preparation that increases the ability of the coating to permeate and adhere to the floor includes roughing the surface of the concrete. This can be accomplished by mechanical grinding, bead blasting, or similar mechanical processes that roughen the surface of the concrete.

Thereafter, in step 140, a thin coating of material is applied upon the top layer of concrete foundation that imparts chemical resistance in the concrete. Exemplary of such materials include novolac, vinyl novolac, and related Bisphenol A or Bisphenol F resin-based epoxy coatings. In a preferred embodiment, such coating should be applied to a thickness from between 5-20 mil with 5-10 being preferred, that is relatively thin and absorbs into concrete. Such coating is thereafter allowed to dry.

In step 150, a second layer (topcoat) is applied of any of the aforementioned materials, namely novolac, vinyl novolac or related resin-based two-part epoxy coatings. According to a preferred embodiment such second layer is applied in a thickness from between 10-40 mil for a balance of cost and efficacy. As will be appreciated by those skilled in the art, lower thickness limits are defined by minimum performance requirements whereby the upper thickness limits are defined by cost and practicality. In all such applications, however, the diffusion coefficient for target contaminants in the topcoat material is preferably ≦1.0×10-12 m2/sec.

Alternatively, the diffusion coefficient and the thickness of the topcoat should be selected such that steady-state indoor air contaminant concentration will be <10% of the regulatory allowable limit, based on industry standard modeling (e.g. the Johnson-Ettinger Model) for indoor air contamination. One skilled in the art will be farmiliar with modeling of indoor air contamination by various available methods, including the Johnson-Ettinger model. These models use multiple input parameters to calculate the amount of contaminant in building air relative to the amount present beneath the building. Using these methods, along with chemical diffusion coefficients for the coating system, one can calculate the level or protection provided by a topcoat of a given thickness.

Following application of the topcoat, the coatings are allowed to dry forming a protective barrier whereby the process ends at 160. Advantageously, the coatings are expected to last the life of the building, or until physical wear requires repair or replacement.

The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including various ways of preventing intrusion of toxic vapors into a building's interior air space. For example, the materials applied to the concrete foundation may be applied by any of a variety of techniques well-known in the art, such as by rolling, spraying, and the like. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments. 

What is claimed is:
 1. A method for preventing intrusion of toxic contaminants into the interior air space of a building built upon a concrete foundation through which said contaminants permeate and contaminate the interior air space, the method comprising the steps: a. detecting the presence of contaminants within the building's interior air space or in nearby soil or groundwater; b. preparing the top surface of the building's concrete foundation for receiving a topical application of a material; c. applying a first layer of material upon said top surface of said concrete foundation and allowing said first layer to dry; d. applying a second layer topcoat upon said layer formed in step c), said first and second layers reacting with one another to define a material operative to form a barrier preventing said contaminants from permeating through said foundation and into said interior air space of said building.
 2. The method of claim 1 wherein in step a) and d), said materials applied to said concrete foundation chemically resistant two-part epoxy coatings.
 3. The method of claim 2 wherein said chemically resistant two-part epoxy coatings are selected from the group consisting of novolac and vinyl novolac.
 4. The method of claim 1 wherein said first layer is applied to have a thickness from between 5-20 mil and said second layer is applied to have a thickness from between 10-40 mil.
 5. The method of claim 4 wherein said material applied for said first and second layers is selected from the group consisting of novolac, vinyl novolac, Bisphenol A resin-based epoxy coatings, and Bisphenol F resin-based epoxy coatings.
 6. The method of claim 1 wherein in step a, said contaminant is identified as being a contaminant selected from the group consisting of tetrachloroethylene, trichloroethylene, dichloroethylene isomers, vinyl chloride, benzene, toluene, ethylbenzene, xylene isomers, and other chlorinated and petroleum VOCs (volatile organic compounds). 